// SPDX-License-Identifier: GPL-2.0-only /* * Test for find_*_bit functions. * * Copyright (c) 2017 Cavium. */ /* * find_bit functions are widely used in kernel, so the successful boot * is good enough test for correctness. * * This test is focused on performance of traversing bitmaps. Two typical * scenarios are reproduced: * - randomly filled bitmap with approximately equal number of set and * cleared bits; * - sparse bitmap with few set bits at random positions. */ #include <linux/bitops.h> #include <linux/kernel.h> #include <linux/list.h> #include <linux/module.h> #include <linux/printk.h> #include <linux/random.h> #define BITMAP_LEN (4096UL * 8 * 10) #define SPARSE 500 static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata; static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata; /* * This is Schlemiel the Painter's algorithm. It should be called after * all other tests for the same bitmap because it sets all bits of bitmap to 1. */ static int __init test_find_first_bit(void *bitmap, unsigned long len) { unsigned long i, cnt; ktime_t time; time = ktime_get(); for (cnt = i = 0; i < len; cnt++) { i = find_first_bit(bitmap, len); __clear_bit(i, bitmap); } time = ktime_get() - time; pr_err("find_first_bit: %18llu ns, %6ld iterations\n", time, cnt); return 0; } static int __init test_find_next_bit(const void *bitmap, unsigned long len) { unsigned long i, cnt; ktime_t time; time = ktime_get(); for (cnt = i = 0; i < BITMAP_LEN; cnt++) i = find_next_bit(bitmap, BITMAP_LEN, i) + 1; time = ktime_get() - time; pr_err("find_next_bit: %18llu ns, %6ld iterations\n", time, cnt); return 0; } static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len) { unsigned long i, cnt; ktime_t time; time = ktime_get(); for (cnt = i = 0; i < BITMAP_LEN; cnt++) i = find_next_zero_bit(bitmap, len, i) + 1; time = ktime_get() - time; pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt); return 0; } static int __init test_find_last_bit(const void *bitmap, unsigned long len) { unsigned long l, cnt = 0; ktime_t time; time = ktime_get(); do { cnt++; l = find_last_bit(bitmap, len); if (l >= len) break; len = l; } while (len); time = ktime_get() - time; pr_err("find_last_bit: %18llu ns, %6ld iterations\n", time, cnt); return 0; } static int __init test_find_next_and_bit(const void *bitmap, const void *bitmap2, unsigned long len) { unsigned long i, cnt; ktime_t time; time = ktime_get(); for (cnt = i = 0; i < BITMAP_LEN; cnt++) i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1); time = ktime_get() - time; pr_err("find_next_and_bit: %18llu ns, %6ld iterations\n", time, cnt); return 0; } static int __init find_bit_test(void) { unsigned long nbits = BITMAP_LEN / SPARSE; pr_err("\nStart testing find_bit() with random-filled bitmap\n"); get_random_bytes(bitmap, sizeof(bitmap)); get_random_bytes(bitmap2, sizeof(bitmap2)); test_find_next_bit(bitmap, BITMAP_LEN); test_find_next_zero_bit(bitmap, BITMAP_LEN); test_find_last_bit(bitmap, BITMAP_LEN); /* * test_find_first_bit() may take some time, so * traverse only part of bitmap to avoid soft lockup. */ test_find_first_bit(bitmap, BITMAP_LEN / 10); test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); pr_err("\nStart testing find_bit() with sparse bitmap\n"); bitmap_zero(bitmap, BITMAP_LEN); bitmap_zero(bitmap2, BITMAP_LEN); while (nbits--) { __set_bit(prandom_u32() % BITMAP_LEN, bitmap); __set_bit(prandom_u32() % BITMAP_LEN, bitmap2); } test_find_next_bit(bitmap, BITMAP_LEN); test_find_next_zero_bit(bitmap, BITMAP_LEN); test_find_last_bit(bitmap, BITMAP_LEN); test_find_first_bit(bitmap, BITMAP_LEN); test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); /* * Everything is OK. Return error just to let user run benchmark * again without annoying rmmod. */ return -EINVAL; } module_init(find_bit_test); MODULE_LICENSE("GPL");